Classified abstracts 1180--1192 7-25 kOe, initial hydrogen pressure of 10-4-10 -2 torr and discharge current of 7-35 kA. The experimental results are discussed. G A Bobrovskiy et al, Zh Eksper Teor Fiz, 59 (10), Oct 1970, 11031114 (in Russian). 32 1180. Helium negative ion source for a charge exchange electrostatic accelerator. (USSR) A helium negative ion source with current of 8/~A is described. To obtain helium negative ions, charge exchange of He + on caesium vapour stream is employed. Yu M Khirnyy and L N Kochemasova, Prib Tekh Eksper, No 1, 1971, 37-39 (in Russian). 32 1181. A source of polarized negative deuterium ions for a charge exchange electrostatic accelerator. (USSR) A source of polarized negative deuterium ions with current of 4 × 10-s A is described which is based on generation of negative deuterium ions on a caesium vapour stream target. Yu M Khirnyy and L N Kochemasova, Prib Tekh Eksper, No 1, 1971, 39-44 (in Russian). 32 1182. Arrangement for continuous pumping of gas through a proportional counter at various pressures. (USSR) A n arrangement with a pump, for continuous pumping of gas through a proportional counter in the pressure interval from 0.5 to 1500 torr, is described. The proportional counter can also be used as a gas purity monitor in a system for gas purification. Yu I Bregadze and P F Maslyaev, Prib Tekh Eksper, No 1, 1971, 70-71
(in Russian). 32 1183. Utilization of thin organic layers in nuclear physics experiments. (USSR) Possibility of utilizing thin organic layers in the windows for gas targets in nuclear physics experiments is investigated. Mechanical strength and permeation rate for various organic layers with thickness of 1 to 2/zm are investigated using a helium mass-spectrometer leak detector. I Ya Barit et al, Prib Tekh Eksper, No 1, 1971, 57-60 (in Russian). 32 1184. Field electron gun for linear electron accelerator. (USSR) Construction of a field electron gun is described which is used for injection of electron clusters in a linear electron accelerator. Experimental examinations showed that the gun gives an electron beam with 1 A pulsed current and energy of 500 keV at an applied ultrahighfrequency power of 1 MW. A tungsten tip emitter is used and a pressure of 2 × 10 -e torr is maintained in the resonator with the aid of two electrical-discharge pumps. B Yu Bogdanovich et al, Prib Tekh Eksper, No 1, 1971, 44-46 (in
Russian). 32 1185. A long-lived radio-frequency ion source of low consumption for pressurized accelerators. (Hungary) A radio-frequency ion source with extraction electrodes located outside the discharge tube is described. A focused ion beam with an intensity of 10-100 ttA and with a 57 per cent H + ion content is obtained by using a static transverse magnetic field. Excellent stability for many hundred hours together with its mechanical construction permitted the use of this source in a 1 MeV pressurized Van de Graaff accelerator. I L Nagy, Acta Phys Acad Sci Hung, 28 (1-3), 1970, 269-277. 33. GENERAL PHYSICS AND ELECTRONICS 33 1186. Method of measuring the rigidity of the tubular cores of heated electronic-valve cathodes. (USSR) A method of measuring the rigidity of the tubular cores of heated electronic-valve cathodes under conditions closely simulating those governing the practical use of the cathodes is described. Thus a bending force is applied to the cathode in a manner simulating the forces of thermal expansion which change the cathode-grid distance in the valve under working conditions and sometimes lead to a short circuit between these components. The rigidity may be calculated from the displacements so induced by applying a simple mechanical formula. B Kh Katsnel'son, USSR Patent, No 270,008, appl 23rd April 1968, publd 30th July 1970.
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33 1187. Cathode. (USSR) A n improved form of cathode for use in electronic valves and also thermoelectric energy converters is described. The new cathode differs from conventional rhenium and hafnium-base cathodes (which have a relatively low emission) in containing an yttrium additive (0.5-35 at. per cent). This alloy gives a secondary-emission coefficient of 1.8 (instead of 1.7) and has a work function of 3.1 eV (instead of 3.85) for a working temperature of no higher than 1800°C. The rhenium-yttrium alloy is not toxic, it requires no special activation, and its emission characteristics remain stable under electron bombardment. A A Gugnin et al, USSR Patent, No 250,323, appl 15th Dec 1964, publd 30th April 1970. 33 1188. A cathode for electrical-vacuum devices. (USSR) A new type of rhenium-base cathode for use in electrical-vacuum apparatus is described. The cathode differs from existing types in that it contains 1-10 wt. per cent of zirconium. The alloy has a work function of 3.6 eV (as judged by the normal Richardson straight lines) and a maximum secondary-emission coefficient of 1.72, these parameters being constant up to 2000°C. In addition to its high emission, the alloy has high electrical and thermal conductivities; the emission remains stable under electron bombardment. A A Gugain et al, USSR Patent, No 268,553, appl 18th June 1964, publd lOth Sept 1970. 33 1189. Method of preparing electronic devices. (USSR) A method of increasing the accuracy of maintaining the designed inter-electrode distances in the manufacture of electronic devices is described. Thus one of the electrodes, capable of being moved relative to the insulator during the sealing of the device, is used as a base surface, and the other electrodes are bracketed on to the first in such a way that, after the completion of soldering or welding operations and the return of the system to room temperature, the pre-specified interelectrode distances are taken up, independently of any slight random variations in the dimensions of individual electrodes. Yu P Dyagilev, USSR Patent, No 272,995, appl 25th Dec 1967, publd 8th Oct 1970. 33 1190. Effects of surface disorder, various surface structures of chemisorbed gases and carbon on helium atomic beam scattering from the (100) surface of platinum. (USA) LEED and helium atomic beam scattering were combined to study the effects of changing surface structure on the gas-solid interaction for the (100) face of a platinum single crystal. The angular distribution of a helium beam scattered from the ordered and disordered crystal face was monitored. The intensity of the beam scattered at the specular angle increases by nearly an order of magnitude upon atomic ordering of the metal surface. The magnitude of the intensity maxima for helium beams scattered from ordered surface structures of various chemisorbed gases (CO, CaH2) was sensitive to surface order but insensitive to the type of surface structure formed. In order to carry out the studies, U H V conditions ( < 1 0 -8 torr) were maintained in the scattering chamber. Details of the apparatus are given. L A West and G A Somorjai, J Chem Phys, 54 (7), 1st April 1971, 2864-2873. 33 1191. New method for the detection of atomic oxygen beams Atomic oxygen adsorbed on ZnO single crystals causes a decrease of surface conductivity. This fact is used to measure the flux density of atomic oxygen. With a surface detector of 0.3 m m ~ the lower limit of detection is 1 × 10u atoms sec -~ cm -2. The method of making ZnO crystals and providing gold contacts is described. An atomic beam apparatus making use of the Stern-Gerlach effect was used for the measurements. Details of procedure are given. H Nahr et ai, J Chum Phys, 54 (7), 1st April 1971, 3022-3025. 33 1192. Chemisorptive luminescence: oxygen on Si (111) surfaces. (USA) This luminescence is a diffuse gas-phase emission extending 2-3 cm above the crystal surface. The spectrum appears continuous, in low resolution, throughout the visible. About 1 in 10 7 0 z absorptions produces a photon and no emission is seen during chemisorption of